Reversible Thermochromism of Nickel(II) Complexes and Single-Crystal-to-Single-Crystal Transformation

A molecular Ni­(II)–NNN pincer complex (1) exhibited unprecedented reversible single-crystal-to-single-crystal transformation and color change upon heating and cooling due to a subtle change in the N–Ni­(II) bond length and ligand conformation. UV–vis, thermogravimetric, differential scanning calorimetry, single-crystal structural data, temperature-dependent powder X-ray diffraction, and Raman and computational studies supported the structural change of the Ni­(II) complex with temperature.